Given half a chance, my 11-year-old would spend hours with his eyes fixed to a screen, hands working frantically at the controller, oblivious to the outside world. Just like a million other kids. And, like a million other parents, I worry about it. So imagine my delight - not to mention scepticism - at finding a book, Everything Bad Is Good for You, which says that my son is actually improving his mind. And the author is no wishful-thinking game-addicted twentysomething, but a respected academic and father of two. When I met him in London, he seemed entirely sane.

"That fixated look the kids get is a look of focus, not of being a zombie," says Steven Johnson, author and lecturer in interactive telecommunications at New York University. "It's a brain working hard." Today's games are complex, he says, and parents should have a go at them: "You'll find they're both more entertaining and more difficult than you expect."

Recent research shows that video games can improve visual intelligence and hand-eye coordination, but Johnson goes further. He thinks they increase IQ. There is an upward trend in American IQ scores - the kind based on abstract graphics and pattern-spotting - and Johnson believes this is due to the nature of modern popular culture, to the brain development gained from interactive media. Not only do most games require you to remember multiple combinations of buttons (and use them fast), but often there are few established rules. Adults are likely to say: "What am I supposed to do?"

"It's as if each time you start a game of chess, the moves have been scrambled and there are no instructions," says Johnson. "When you make a move, you get feedback and you have to work out the moves and the rules as you play the game."

Johnson calls this process "probing". It is followed, he says, by "telescoping" - prioritising multiple objectives into a scheme to get you to the final goal. "These are raw skills that can be applied to other parts of life," he says, "core building blocks of what it means to be smart. People who are successful in life are good at these things."

And the games are far from instant gratification, Johnson insists. "There are a lot of chores in games. In fact, in The Sims [where you control the lives of a group of people], you have to do real chores like clearing the dinner off the table, otherwise flies get at it, the people aren't happy and you do badly at the game."

I don't notice my son instantly clearing the dinner from the real table, or "probing" and "telescoping" the actions necessary to be able to play his violin perfectly, but Johnson shrugs and grins: kids will be kids.

He is not claiming that games are as challenging as learning a musical instrument; merely that they are more challenging than other forms of popular entertainment. "Kids today are doing more intellectually rigorous things than we were," Johnson says. "If we were sitting round in the 70s reading Middlemarch all day, perhaps that wouldn't be true, but most of us were watching Charlie's Angels."

But wouldn't Johnson rather his child read a book than play a video game? No, he insists, games teach you things a book won't. Of course, he adds, you won't get from games what you can get from books: narrative, cogent argument, understanding of the human psyche. "I am a huge fan of books. I write books for a living. Kids should be encouraged to read." And also, he agrees, to play outside, talk to friends and do their homework.

Johnson does recognise the perennial problem of peeling kids away from the screen to do these other things: "Games have an amazing power over a mind. Part of that is healthy. It gets kids thinking in a rigorous way. But there is a dark side: suddenly it's five hours later and they've forgotten about real life. Parents have to be strict about that. Tell them, 'I'm not saying your games are worthless, but they can be addictive and you have to be careful.' "

Which goes for adults, too. If you intend to follow another of Johnson's suggestions, to join your kids in the game, then beware! My husband did this - and the kids loved it - but he became so involved that he was to be found playing alone long after the boys were in bed.

Even if we accept that games are mind-stretching, aren't some of them just too violent? Johnson says content should be age-appropriate. He wouldn't give his four-year-old Grand Theft Auto (a violent game in which you try to build a criminal empire), but he adds, "If you've got a 17-year-old who is watching Martin Scorsese movies, then I wouldn't panic if he's playing this game." Ultimately, the value of games is not in their content, Johnson stresses; that would be like wanting chess to teach morality. "Games are not about what you are doing; they're about the way you have to think to do them."

Rather than trying to pull the child off the computer all the time, Johnson suggests, parents should encourage them to play games that are mentally stimulating. He recommends "the god games": Sim City (his favourite, in which you build a city from scratch), The Sims, Age of Empires, Civilisation and Black and White (in which you actually play a god). The Nintendo Zelda games are full of challenging puzzles, and some of the more sophisticated sports simulations, in which you manage teams, "are like a business school education".

"The ones I object to are the first-person shooters where all you do is go around firing," he says. "You won't get anything out of that but hand-eye coordination." Johnson would like to see games rated not just for content but also by their cognitive engagement.

The bestselling games, Johnson points out, are usually the most complex. Gamers are not would-be zombies after all, but are looking for a challenge. Parents and teachers need to recognise the strengths of popular culture and what it is teaching our children, but also recognise what it does not teach. We need to fill the gaps, he says, particularly in verbal and emotional intelligence and social skills. Although he observes that given the chance, children will play video games in groups, and interact with each other as much as with the game.

So what will I do with my 11-year-old? My new plan is to stop running down his game-playing, look a little more closely at the games he is choosing, and stick to my guns when it's time to turn the thing off and do something else.

· Everything Bad is Good for You, by Steven Johnson, is published by Allen Lane, price £10